Cylinder head discussion 340 with stock above deck pistons

First off is you need to be launching the car at a higher rpm, at least 5000 and ride the clutch out far enough so as to not let the rpm's drop more then a 1000 rpm's. If you have the close ratio 4 spd, then you have a 2.47 first gear coupled with a 3.55 rear gear give you a 8.76 starting ratio(not a good ratio to get off the line cleanly with) without slipping the hell out of the clutch. Get rid of the radials and put a short bias ply slicks on the car.
When you get to the point where you can keep the engine from bogging and keep the engine at peak torque or higher by slipping the clutch. The car shound 60 ft. good enough with the setup you have now to run in the 12's.